The present invention relates to an optical mirror switch and, more particularly, to an optical mirror switch based upon an optical implementation of a Michelson interferometer.
Conventional electro-optical switches can be realized using a number of different waveguide, electrode, and substrate implementations. Two different designs are used in commercially available electro-optical switches; the Mach-Zehnder and the .DELTA..beta. directional coupler. The Mach-Zehnder design is similar to that of a free-space, conventional Mach-Zehnder interferometer, except that the beam splitters/combiners are replaced by 3-dB directional couplers. Similar to the Mach-Zehnder, the first 3-dB coupler splits the incident signal into two signals, ideally of equal intensity. If a differential phase shift is introduced between these signals, then when they re-combine in the second 3-dB coupler, the ratio of power in the two outputs will be altered. Contrast ratios greater than 20 dB (e.g., 100:1) are routinely achieved in commercial devices. In the .DELTA..beta. directional coupler switch, electrodes are placed directly over (or immediately next to) the coupler and an applied electric field functions to alter the power transfer between the two adjacent waveguides. The contrast ratios achieved with the .DELTA..beta. directional coupler switch are comparable to those of the 3-dB coupler arrangement.
A "mirror" switch can be defined as an arrangement including a pair of bidirectional ports. In a first state of the mirror switch, the ports are directly coupled to each other (a "pass" state). In a second state (hereinafter referred to as the "reflective" state), the ports are de-coupled so that an input signal is directly reflected and then returned back through the same port, that is, an optical signal input into the first port would be reflected back into the first port and, optionally, an optical signal input into the second port would be reflected back into the second port.